On Tue, 2008-02-26 at 13:56 -0800, James Bottomley wrote: > > Our iommu can use smaller than PAGE_SIZE allocations when PAGE_SIZE is > > 64k (it can use 4k), and that helps a lot with networking to avoid > > filling up pSeries small iommu's too fast. Unfortunately, that meant we > > used to not even get PAGE_SIZE alignment for some cases. The workaround > > fixes that but does not provide natural size alignment. > > > > If we were to provide size based alignment of sg requests, fragmentation > > would become so bad we would basically end up failing a large amount of > > iommu allocations on servers. > > Ben, he just quoted the wrong patch ... that was the segment length > limit patch. The boundary alignment patch is this one: > > fb3475e9b6bfa666107512fbd6006c26014f04b8 > > And it does alter the ppc iommu to respect the dma_boundary, so all of > the mechanics for removing the ppc special casing in libata/ide is > upstream. And the fact that this will totally blow fragmentation through the roof and cause half of the dma-map requests to fail on machines with small iommu has been totally ignored I suppose ? Ben. - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
